The New York State Senate on Tuesday evening voted to expel Senator Hiram Monserrate, the first removal of a member of the State Legislature in nearly a century.
Mr. Monserrate, a Democrat from Queens, was found guilty of misdemeanor assault of his girlfriend in October.
Rather than bringing a close to Mr. Monserrate’s legislative career, the expulsion could be the beginning of a lengthy fight that would play out in the courts and create further instability in the already volatile political atmosphere in Albany.
As the Senate moved forward with a vote, Mr. Monserrate’s lawyers were drafting a temporary restraining order seeking to have him reinstated. One of the lawyers, Norman Siegel, said the order would be filed Wednesday in federal court in Manhattan.
“This case raises substantial questions concerning what a constitutional democracy is all about,” Mr. Siegel said. “The New York State Senate does not have the constitutional and legal authority to expel Senator Monserrate. And even if they did, their actions have not been consistent with due process of law.”
The expulsion followed roughly five hours of closed-door negotiations among Senate Democrats, though Mr. Monserrate was asked to leave the room for part of the deliberations.
“Nobody was happy about this,” said Senator Eric T. Schneiderman, the Manhattan Democrat who led the special committee that recommended that the Senate consider expelling Mr. Monserrate. “But most senators on both sides of the aisle felt that we had to do something. The days of sweeping things under the rug are over.”
Few other episodes have so grimly symbolized Albany’s reputation as a place where impropriety and ethically questionable conduct among public officials is commonplace.
As a member of a fragile Democratic majority that holds power by a single vote, Mr. Monserrate used the threat that he would switch political allegiances to gain considerable leverage within his party. After he was arrested in December 2008 and details of the assault became known, no Democrats in the Senate openly criticized his conduct. He was given a committee chairmanship, though it was revoked after his indictment, and was even the beneficiary of a fund-raiser by the majority leader at the time, Senator Malcolm A. Smith of Queens.